Moving object detecting apparatus, moving object detecting method, pointing device, and storage medium

ABSTRACT

Even when a user is gazing at one point intentionally but the eyeball of the user is actually moving slightly, the slight movement is not reproduced as it is as the position of a cursor but a determination is made that the user is gazing at one point intentionally, that is, the eyeball is stopping. Thus, when a determination is made that the eyeball is stopping, the cursor is displayed still even when the gazing point is moving slightly depending on the slight movement. Furthermore, when a determination is made that the cursor is stopped, selection of an object such as other icon displayed at a position where the cursor is displayed is identified.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application claiming thebenefit under 35 U.S.C. §120 of U.S. patent application Ser. No.12/666,222, filed on Dec. 22, 2009, now U.S. Pat. No. 8,717,292, whichin turn is a U.S. national stage application under 35 U.S.C. §371 ofInternational Application No. PCT/JP2007/065404, filed on Aug. 7, 2007.The entire contents of both U.S. patent application Ser. No. 12/666,222and International Application No. PCT/JP2007/065404 are incorporatedherein by reference in their entirety.

BACKGROUND

The present invention relates to a moving object detecting apparatusthat detects a movement of a moving object. Particularly, the presentinvention relates to a moving object detecting apparatus and a movingobject detecting method capable of determining a moving object, which issupposed to be stopping or is moving slightly while it is intended tostop, as it is stopping in accordance with the characteristic of slightmovement of the moving object, a pointing device using the moving objectdetecting apparatus and/or method, a computer program causing a computerto function as the moving object detecting apparatus, and a storagemedium storing the computer program.

DESCRIPTION OF RELATED ART

Technologies have been widely used that detect a movement of a movingobject by using a sensor, determine whether it is moving or not, andperform various controls based on a quantity of movement when it ismoving. The sensor may include an image sensor based on atwo-dimensional image. A technology that detects the movement of amoving object from a discriminative form or contour contained in acaptured image and further detects a spatial movement from a change insize of the discriminative form or contour contained in the capturedimage is disclosed in Japanese Patent Application Laid-Open No.2002-63578.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram illustrating a principle of a pointingdevice according to the present embodiment;

FIG. 2 is a block diagram illustrating an internal configuration of aneye-ball movement detecting apparatus and PC for implementing thepointing device according to the present embodiment;

FIGS. 3A and 3B are schematic diagrams illustrating angles of a line ofsight of a user, which are detected by the eye-ball movement detectingapparatus according to the present embodiment;

FIG. 4 is an explanatory diagram illustrating the principle foracquiring a gazing point of a user by the conversion based on an anglesignal output from the eye-ball movement detecting apparatus accordingto the present embodiment;

FIG. 5 is an explanatory diagram schematically illustrating thereference for determining that an eyeball of a user is stopping by a CPUin the PC according to the present embodiment;

FIG. 6 is a flowchart illustrating a routine of cursor renderingprocessing based on an eye-controlled input by the CPU in the PCaccording to the present embodiment;

FIG. 7 is a flowchart illustrating an example of the processing routinefor calculating a minimum containing circle in the cursor renderingprocessing by the CPU in the PC according to the present embodiment;

FIG. 8 is a flowchart illustrating the example of the processing routinefor calculating a minimum containing circle in cursor renderingprocessing by the CPU in the PC according to the present embodiment; and

FIG. 9 is an explanatory diagram illustrating an example of a locus of acursor displayed based on eye-controlled input with a pointing deviceaccording to the present embodiment.

DETAILED DESCRIPTION

With reference to drawings illustrating an embodiment of the presentinvention, the embodiment will be described more specifically below.Notably, an embodiment as will be described below is an example in whicha pointing device based on an eye-controlled input is implemented byapplying a moving object detecting apparatus to a pointing deviceincluded in a personal computer, detecting a movement of an eyeball (ormovement of a line of sight) of a user with respect to a displayconnected to a personal computer, and displaying a cursor in accordancewith the movement of the eyeball.

FIG. 1 is an explanatory diagram illustrating a principle of a pointingdevice according to the present embodiment. FIG. 1 illustrates animaging apparatus 1 that images a movement of an eyeball of a user. FIG.1 further illustrates an eye-ball movement detecting apparatus 2 thatdetects a movement of an eyeball of a user based on the captured imageinput from the imaging apparatus 1. FIG. 1 further illustrates apersonal computer (PC) 3 to be used by a user. The PC 3 is connected toa display 4, and an image signal representing a display screen includinga GUI (graphical user interface) such as a window and a cursor renderedbased on the operation on the PC 3 is output to the display 4.

The pointing device according to the present embodiment is implementedin accordance with the principle as follows. The eye-ball movementdetecting apparatus 2 detects a movement of an eyeball of a user from acaptured image. A quantity of the movement detected by the eye-ballmovement detecting apparatus 2 is detected as an angle in the horizontaldirection and an angle in the vertical direction of the display 4 of aline of sight of a user about the reference straight line that is astraight line vertically entering the display 4. An angle signalrepresenting the detected horizontal and vertical angles is input fromthe eye-ball movement detecting apparatus 2 to the PC 3. In the PC 3,the angles represented by the input angle signal are converted to apoint of intersection of the line of sight of the user and the display4, that is, a coordinate of a gazing point on the display 4 based on adistance between the eyeball of the user and the display 4. Since thecoordinate acquired by the conversion is the gazing point of the user onthe display 4, the coordinate is associated with the operation of thecursor to be displayed on the display 4.

For example, as illustrated in the explanatory diagram in FIG. 1, a useris initially gazing at the display 4 along the line of sight L1. Thegazing point G1 of the user at that time is acquired by the conversionof an angle of the line of sight L1 about the reference straight line tothe point G1 on the display 4 based on the distance from the eyeball ofthe user to the display 4. When the user moves the line of sight to aline of sight L2 thereafter, the angle of the line of sight about thereference straight line is at any time (or at 30 Hz) converted to thegazing point at the corresponding point in time even while the line ofsight is moving. The display position of the cursor is controlled inaccordance with the gazing point acquired by the conversion at thecorresponding point in time. When the user gazes at the display 4 alongthe line of sight L2, the angle of the line of sight L2 about thereference straight line is converted to the gazing point G2 based on thedistance from the eyeball of the user to the display 4, and the cursoris displayed at the position corresponding to the gazing point G2. Thus,the pointing device based on an eye-controlled input can be implemented.

Notably, in order to make the following description easilyunderstandable, it is assumed that a position of an eyeball of a user ison the reference straight line that is equal to a normal to the display4. The imaging apparatus 1 has a direction, height and position adjustedto image the eyeball of a user.

FIG. 2 is a block diagram illustrating an internal configuration of theeye-ball movement detecting apparatus 2 and PC 3 for implementing thepointing device according to the present embodiment. The eye-ballmovement detecting apparatus 2 includes a control unit 20 that controlsthe following components, a storage unit 21 that stores variousinformation, an image acquiring unit 22 that acquires a captured imageoutput from the imaging apparatus 1, and an output unit 23 that outputsan angle signal representing an angle of a line of sight correspondingto a movement of an eyeball of a user calculated by processing by thecontrol unit 20. The PC 3 includes a CPU 30 (controller), a memory 31applying a DRAM (dynamic random access memory), an SRAM (static randomaccess memory) or the like, an HD (hard disk) 32 that stores variousinformation, a receiving unit 33 that receives an angle signal outputfrom the eye-ball movement detecting apparatus 2, an image output unit34 applying a video card, for example, and an auxiliary storage unit 36that reads data in a storage medium 35 such as a DVD (digital versatiledisk) and a CD-ROM.

The image acquiring unit 22 in the eye-ball movement detecting apparatus2 acquires the captured images of an eyeball of a user imaged at a rateof 30 frames per second (30 Hz), for example. Notably, the capturedimage of an eyeball of a user imaged by the imaging apparatus 1 containsa pupil and a reflected light from a cornea surface as a result of theprojection of near infrared light from the imaging apparatus 1 to aneyeball (which is called Purkinje image). The image acquiring unit 22also acquires the captured image at a rate of 30 frames per second (30Hz).

The control unit 20 in the eye-ball movement detecting apparatus 2 readsand executes a predetermined program stored in the storage unit 21 andthus detects the angle of the line of sight of the user based on thecenter of the pupil in the captured image acquired through the imageacquiring unit 22 and the position of the Purkinje image on the capturedimage. Notably, in order to detect the angle based on the center of thepupil and the position of the Purkinje image on the captured image whenthe line of sight of the user is parallel to the reference straightline, the relationship between the center of the pupil and the positionof the Purkinje image on the captured image and the angle is calibratedin advance. However, since the technology for detecting the angle of theline of sight based on the center of the pupil and the position of thePurkinje image is a known technology, the detail description will beomitted (Refer to Japanese Patent Application Laid-Open No. 2006-87751).

The control unit 20 of the eye-ball movement detecting apparatus 2outputs the angle signal representing the detected angle of the line ofsight of the user through the output unit 23 to the PC 3 every time thecaptured image is acquired at 30 Hz.

The HD 32 in the PC 3 stores a control program 3P causing the CPU 30 toperform processing of converting the angle signal representing the angleof the line of sight of the user to the gazing point on the display 4and associating the result with the cursor display. Notably, the controlprogram 3P is stored in the storage medium 35 such as a DVD and aCD-ROM, and the CPU 30 may read it through the auxiliary storage unit 36from the storage medium 35 and store it in the HD 32.

The CPU 30 reads and executes the control program 3P to receive by thereceiving unit 33 the angle signal output from the output unit 23 in theeye-ball movement detecting apparatus 2 and convert the received anglesignal to the gazing point of the user on the display 4.

The image output unit 34 in the PC 3 receives a rendering signal fordisplaying a GUI (graphical user interface) on the display 4 from theCPU 30, creates an image signal therefrom, and outputs the created imagesignal to the display 4. The CPU 30 reads and executes the controlprogram 3P to input the rendering signal for displaying a cursor at theposition corresponding to the converted gazing point to the image outputunit 34 and causing the image output unit 34 to output the image signal.

Notably, the CPU 30 does not handle the gazing point of the useracquired based on the angle signal received by the receiving unit 33directly as the position for displaying the cursor. Whether the eyeballof the user is stopping or moving, the gazing point on the display 4corresponding to the movement of the eyeball is not handled directly asthe position for displaying the cursor for the reasons below.

The first reason is that, when a user is gazing at one point on thedisplay 4, the gazing point is always moving slightly due to the slightinvoluntary eye movement though the user is intentionally gazing at onepoint. Thus, if the gazing point of the user is handled directly as theposition for displaying the cursor, the cursor being displayed is alwaysmoving slightly. As a result, it is difficult for the user to keepgazing. Notably, the degree of the slight involuntary eye movement mayvary among individuals and vary in accordance with the physicalcondition at the time.

The second reason is that, when something is moving near the gazingpoint, a phenomenon that the line of sight follows the moving object mayoccur. As described in the first reason, the slight involuntary eyemovement causes the cursor to be always moving slightly. Thus, when thegazing point corresponding to the movement of the eyeball of the user ishandled directly as the position for displaying the cursor, it is notonly difficult for the user to keep gazing, but also the line of sightmay follow the cursor being moving slightly and resonate with the slightmovement, and thereby being further difficult for the user to keepgazing.

The third reason is that displaying a cursor always at a gazing pointmay simply fatigue the user's eyes. The user's eyes are fatigued whenthe cursor is moved and displayed faithfully in accordance with themovement of the line of sight of the user even while the user is notgazing.

Thus, a pointing device according to the present embodiment determineswhether an eyeball of a user is stopping or not based on the gazingpoint on the display 4 acquired by the conversion from the anglecorresponding to the movement of the eyeball of a user, as will bedescribed later. Furthermore, when it is determined that the eyeball isstopping, the pointing device according to the present embodiment causesthe cursor to be displayed as it is stopping even when the gazing pointacquired by the conversion according to the slight movement of eyeballof the user is moving slightly on the display 4. Also when it isdetermined that the eyeball of the user is not stopping but is moving,the pointing device displays the cursor on a smooth locus like theBezier curve based on the gazing points of the user, instead ofdisplaying the cursor on the locus connecting the gazing points by theuser as they are. Notably, the locus of the cursor to be displayed whenit is determined that an eyeball of a user is moving is not limited tothe Bezier curve but may be a smoothed locus.

Here, a method for determining by the CPU 30 in the PC 3 whether aneyeball of a user is stopping or not will be described. First of all,the processing of converting an angle for acquiring a gazing point of auser on the display 4 will be described.

FIGS. 3A and 3B are schematic diagrams illustrating angles of a line ofsight of a user, which are detected by the eye-ball movement detectingapparatus 2 according to the present embodiment. FIG. 3A illustrates thehorizontal component θx to the display 4 of an angle between thereference straight line entering vertically the display 4 and line ofsight, and FIG. 3B illustrates a vertical component θy to the display 4of the angle between the reference straight line and the line of sight.Notably, the horizontal component θx of an angle between the referencestraight line and the line of sight takes a positive value in the frontright direction of the display 4, and the vertical component θy takes apositive value in the front upper direction of the display 4. Thus,since the vertical component θy illustrated in the schematic diagram inFIG. 3B directs to the lower part than the reference straight line, ithas a negative value. The angle signal representing the θx and θyillustrated in FIGS. 3A and 3B based on the image resulting from theimaging of the eyeball of the user is output by the eye-ball movementdetecting apparatus 2.

FIG. 4 is an explanatory diagram illustrating the principle foracquiring a gazing point of a user by the conversion based on the anglesignal output from the eye-ball movement detecting apparatus 2 accordingto the present embodiment. The explanatory diagram in FIG. 4 illustratesthe principle for converting an angle of a line of sight of a user to agazing point on the display 4 when the reference straight line entersvertically the center of the display 4 and an eyeball of a userpositions at a position away from the reference straight line on thedisplay 4 by a distance d. In the PC 3, a plane coordinate system isdefined in which the center of the display 4 is the origin, and theright direction is the positive direction with the X-axis in thehorizontal direction of the display 4 and the upper direction is thepositive direction with the Y-axis in the vertical direction of thedisplay 4. The CPU 30 converts the horizontal component θx and verticalcomponent θy of the angle between the reference straight line and theline of sight, which are represented by the angle signal output from theeye-ball movement detecting apparatus 2 to the coordinate (x,y)representing the gazing point on the plane coordinate system based onthe following expressions (1) and (2).x=d×tan θx  (1); andy=d×tan θy  (2)

Notably, in the explanatory diagram illustrated in FIG. 4, the line ofsight has an angle from the reference straight line in the upper rightdirection from the user's viewpoint. Since the components θx and θy havethus positive values, positive values are calculated for both of thex-component and y-component of the coordinate representing the gazingpoint. The gazing point of the user is identified as positioning in thefirst quadrant of the plane coordinate system.

Next, the processing will be described for determining whether aneyeball of a user is stopping or not, that is, whether the user intendsto gaze one point or not from the coordinate on the display 4 of agazing point of a user acquired based on the principle as illustrated inFIGS. 3A, 3B, and FIG. 4.

FIG. 5 is an explanatory diagram schematically illustrating thereference for determining that an eyeball of a user is stopping by theCPU 30 in the PC 3 according to the present embodiment. The explanatorydiagram in FIG. 5 illustrates black circle marks and white circle marksindicating gazing points of a user on the display 4, a “+ (plus)” markindicating the center point of the containing circle (which is thecircle drawn by the solid line) having a minimum area that contains allof the gazing points indicated by the white circle marks and blackcircle marks. Even when a user intends to gaze one point on the display4, the gazing points of the user are scattered as illustrated in theexplanatory diagram in FIG. 5 due to the slight involuntary eyemovement. Accordingly, the CPU 30 in the PC 3 calculates the containingcircle having a minimum area containing all of the latest 10 gazingpoints, for example, as illustrated in FIG. 5, determines whether thecoordinate of the gazing point of the user converted from the anglesignal received next are contained in the calculated containing circleor not and thus determines whether the eyeball of the user is stoppingor the user intends to gaze one point or not. The containing circlehaving a minimum area is calculated by, according to the presentembodiment, calculating containing circles containing all of the latest10 points among the circles having as their diameters the linesconnecting arbitrary two points of the latest 10 points and extractingthe containing circle having a minimum diameter from the calculatedcontaining circles. The explanatory diagram in FIG. 5 illustrates thatthe circle having as its diameter the line connecting the two pointsindicated by the white circle marks is calculated as a minimumcontaining circle.

When it is determined that the eyeball of the user is stopping based onthe criterion illustrated in FIG. 5, that is, while the calculatedcontaining circle is containing the gazing points of the user, the CPU30 stops and displays the cursor at the center point of the calculatedcontaining circle. On the other hand, when the next acquired gazingpoint of the user is not contained in the containing circle, the CPU 30determines that the eyeball of the user is moving, calculates the locusof the Bezier curve from the center point of the containing circle tothe next gazing point of the user, and displays the cursor on the locus.

Notably, when it is determined whether an eyeball of a user is stoppingor not based on the criterion illustrated in the explanatory diagram inFIG. 5 at all times from the beginning of the processing, the containingcircle is calculated based on the latest gazing points while the user ismoving the line of sight intentionally and is moving the eyeball as aresult. Then, there is a possibility that a large containing circleoccupying the most part of the display 4 may be calculated as thecriterion. In this case, the gazing point may not be released from thecontaining circle that is the criterion for determining whether theeyeball is stopping or not, and the cursor may always be displayed atthe center point of the containing circle. In order to solve this, amaximum value and a minimum value of the diameter of the containingcircle being the criterion are predefined. Thus, when the diameter ofthe calculated containing circle exceeds the predefined maximum value,the containing circle is not used as the criterion for determiningwhether the eyeball is stopping or not, and it is determined that theeyeball of the user is moving.

According to the present embodiment, based on the determination whethera gazing point of a user is contained in a figure having a predeterminedarea for a predetermined period of time or longer or not, the CPU 30 inthe PC 3 primarily determines whether the possibility that the eyeballof the user may be stopping is high or not. When the gazing point of theuser is contained in the figure having the predetermined area for thepredetermined period of time or longer, the CPU 30 calculates thecontaining circle containing the predetermined number of latest gazingpoints again and then determines whether the eyeball of the user isstopping or not based on the calculated containing circle.

Next, the cursor rendering processing based on the above criterion willbe described with reference to flowcharts. FIG. 6 is a flowchartillustrating a routine of cursor rendering processing based oneye-controlled input by the CPU 30 in the PC 3 according to the presentembodiment.

The CPU 30 receives an angle signal through the receiving unit 33 fromthe eye-ball movement detecting apparatus 2 (step S101), converts theangle represented by the received angle signal to the coordinaterepresenting the gazing point on the plane coordinate system on thedisplay 4 (step S102). The CPU 30 stores the coordinate resulting fromthe conversion in the memory 31 temporarily (step S103), and determineswhether a movement of an eyeball of a user based on the immediatelypreceding gazing point results in that the eyeball is stopping or not,that is, whether the user is gazing at one point or not (step S104).

When the CPU 30 determines in step S104 that the movement base on theimmediately preceding gazing point does not result in that the eyeballis stopping (S104 NO), the CPU 30 determines whether the coordinatesrepresenting the gazing points within the predetermined latest period oftime (such as 600 millisecond) are contained within a predeterminedrange (such as within a rectangle of 10×10 pixels) or not (step S105).When the CPU 30 determines that the coordinates representing the gazingpoints within the predetermined latest period of time are not containedwithin the predetermined range (S105 NO), the CPU 30 determines that theeyeball is moving (step S106). In this case, the CPU 30 performsrendering processing for displaying a cursor on the locus forming theBezier curve corresponding to the coordinate acquired in step S102 (stepS107), deletes the coordinates representing the oldest gazing pointamong the past coordinates beyond a predetermined number (such as 10points) from the memory 31 (step S108), and ends the processing.

When the CPU 30 determines in step S105 that the coordinates within thepredetermined latest period of time are contained in the predeterminedrange (S105 YES), the CPU 30 calculates the center and radius (ordiameter) of the containing circle having a minimum area containing allof the predetermined number (such as 10) of latest coordinates andstores them in the memory 31 (step S109). The CPU 30 determines that thecoordinate acquired in step S102 is contained in the minimum containingcircle calculated in step S109 or not (step S110).

When the CPU 30 determines that the coordinate calculated in step S102is not contained in the minimum containing circle stored in the memory31 (S110 NO), the CPU 30 determines that the eyeball is moving (S106).Then, the CPU 30 performs rendering processing for displaying a cursoron the locus rendering the Bezier curve corresponding to the acquiredcoordinate (S107), deletes the coordinate representing the oldest gazingpoint from the memory 31 (S108), and ends the processing.

When the CPU 30 determines that the coordinate acquired in step S102 iscontained in the minimum containing circle stored in the memory 31 (S110YES), the CPU 30 determines that the eyeball is stopping (step S111). Inthis case, the CPU 30 performs rendering processing for display a cursorat the center point of the minimum containing circle (S107), deletes thecoordinate representing the oldest gazing point from the memory 31(S108), and ends the processing.

When the CPU 30 determines that the movement base on the immediatelypreceding gazing point results in that the eyeball is stopping in stepS104 (S104: YES), the processing moves to step S110 where the CPU 30determines whether the minimum containing circle calculated lately andstored in the memory 31 contains the coordinate acquired in step S102 ornot (S110). Then, the CPU 30 performs the subsequent processing (fromstep S106 to step S108 or from step S111 and step S107 to step S108).

In order to perform the determination processing in step S105, the CPU30 starts the processing in the flowchart in FIG. 6 after a lapse of atleast 100 milliseconds from the first reception of the angle signal(when at least three coordinates exist as a result of the conversion atevery 30 Hz).

Notably, the CPU 30 repeats the processing routine illustrated in theflowchart in FIG. 6 in the same timing of 30 Hz as the rate forreceiving the angle signals from the eye-ball movement detectingapparatus 2.

In the processing illustrated in the flowchart in FIG. 6, when the CPU30 in the PC 3 determines in step S104 that the movement base on theimmediately preceding gazing point results in that the eyeball isstopping and determines even once that the coordinate acquired from thereceived angle signal is not contained in the minimum containing circle,the CPU 30 determines that the eyeball of the user is moving and theuser intends to move the line of sight. However, without limitingthereto, when the CPU 30 determines that the coordinates representingthe gazing points are not contained in the minimum containing circleplural times, the CPU 30 may determine that the eyeball is moving. Thus,even when the gazing point once leaves the minimum containing circle andthe gazing point moves slightly again within the minimum containingcircle due to the saltatory and slight movement of the eyeball likeflicker or when it is detected that the eyeball is moving slightly dueto a detection error on the angle by the eye-ball movement detectingapparatus 2, it may be determined that the eyeball is stopping.

The processing illustrated in the flowchart in FIG. 6 allows thedetermination whether an eyeball of a user is stopping or not inaccordance with the characteristic of the slight involuntary eyemovement which varies depending on an individual and also depending onthe physical condition at the time of the individual. Whether theeyeball is stopping or not may be determined based on whether the gazingpoint is contained in a figure having a predetermined size with respectto some reference or not. However, in that case, in accordance with somecharacteristics of the slight movement which varies depending on anindividual and also depending on the physical condition at the time ofthe individual, the slight movement of the eyeball, which is supposed tobe determined as stopping may be determined as moving. In the case withthe processing illustrated in the flowchart in FIG. 6, the criterion tobe used after that for determining whether the eyeball is stopping ornot is determined based on the predetermined number of actual latestgazing points. Therefore, in accordance with the characteristic of theslight involuntary eye movement which varies due to an individualdifference and also depending on the physical condition at the time ofthe individual, the state that the eyeball is stopping, that is, theuser is intentionally gazing one point can be determined.

FIG. 7 and FIG. 8 are flowcharts illustrating an example of theprocessing routine for calculating a minimum containing circle in cursorrendering processing by the CPU 30 in the PC 3 according to the presentembodiment. Notably, the processing routine illustrated in theflowcharts in FIG. 7 and FIG. 8 corresponds to the details of theprocessing for calculating a minimum containing circle in step 8109within the processing routine illustrated in the flowchart in FIG. 6.

The CPU 30 selects arbitrary two points from the predetermined number(such as 10) of latest coordinates among the coordinates representingthe gazing points stored in the memory 31 (step S201) and calculates thecircle having the line connecting the selected two points as a diameter(step S202). Next, the CPU 30 determines whether the calculated circlecontains all of the predetermined number (such as 10) of latest pointsor not (step S203).

When the CPU 30 determines that the calculated circle does not containany of the predetermined number of latest points (S203 NO), the CPU 30returns the processing to step S201 and selects other arbitrary twopoints (S201) and performs the subsequent processing.

When the CPU 30 determines that the calculated circle contains all ofthe predetermined number of latest points (S203 YES), the CPU 30 storesthe center and radius of the calculated containing circle in the memory31 (step S204).

The CPU 30 next determines whether all combinations of the two pointshave been selected from the predetermined number of latest coordinatesamong the coordinates representing the stored gazing points in step S201or not (step S205). When the CPU 30 determines that all of thecombinations have not been selected (S205 NO), the CPU 30 returns theprocessing to step S201, selects other arbitrary two points (S201), andperforms the subsequent processing.

When the CPU 30 determines that all of the combinations have beenselected (S205 YES), the CPU 30 determines whether any containing circleis stored in the memory 31 or not (step S206). That is, the CPU 30determines in step S206 whether the circle having the line connectingany two points within the predetermined number of latest coordinates asits diameter and containing all of other coordinates exists or not.

When the CPU 30 determines that at least one containing circle is stored(S206 YES), the CPU 30 extracts the containing circle having a minimumdiameter from the stored containing circles (step S207), ends theprocessing for calculating the minimum containing circle, and returnsthe processing to step S110 illustrated in the flowchart in FIG. 6.

When the circle having the line connecting any two points within thepredetermined number of latest coordinates as its diameter andcontaining all of other coordinates does not exist, the CPU 30 nextcalculates a minimum containing circle based on three points.

When the CPU 30 determines no containing circle is stored (S206 NO), theCPU 30 selects arbitrary three points from the predetermined number oflatest coordinates within the coordinates representing the gazing pointsstored in the memory 31 (step S208) and calculates the circumscribingcircle of the triangle formed by the selected three points (step S209).The CPU 30 determines whether the calculated circumscribing circlecontains all of the predetermined number (such as 10) of latest pointsor not (step S210).

When the CPU 30 determines that the calculated circumscribing circledoes not contain any of the predetermined number of latest points (S210NO), the CPU 30 returns the processing to step S208, selects otherarbitrary three points (S208), and performs the subsequent processing.

When the CPU 30 determines that the calculated circumscribing circlecontains all of the predetermined number of latest points (S210 YES),the CPU 30 stores the center and radius of the calculated circumscribingcircle as the containing circle in the memory 31 (step S211).

The CPU 30 next determines whether all combinations of three points havebeen selected from the predetermined number of latest coordinates withinthe coordinates representing the stored gazing points in step S208 ornot (step S212). When the CPU 30 determines that all of the combinationshave not been selected (S212 NO), the CPU 30 returns the processing tostep S208, selects other arbitrary three points (S208), and performs thesubsequent processing.

When the CPU 30 determines that all of the combinations have beenselected (S212 YES), the CPU 30 extracts the containing circle having aminimum diameter among the containing circles stored in the memory 31(S207), ends the processing for calculating the minimum containingcircle and returns the processing to the step S110 illustrated in theflowchart in FIG. 6.

The processing for calculating a minimum containing circle mayalternatively include first calculating a circle having a predetermineddiameter, determining whether the calculated circle contains all of thecoordinates representing some latest gazing points or not, and, whennot, determining again whether the calculated circle having an increaseddiameter contains all of the coordinates representing some latest gazingpoints or not, or, when so, determining again whether the calculatedcircle having a reduced diameter contains all of the coordinatesrepresenting some latest gazing points or not. Thus, by repeating theprocessing, a minimum containing circle can be calculated. However, ahigher processing speed can be expected from the calculation of aminimum containing circle by the processing routine illustrated in theflowchart in FIG. 7 and FIG. 8.

FIG. 9 is an explanatory diagram illustrating an example of the locus ofa cursor displayed based on eye-controlled input with a pointing deviceaccording to the present embodiment. The explanatory diagram in FIG. 9shows a movement of a gazing point corresponding to a movement of aneyeball of a user until the user intentionally gazes an iconrepresenting a folder displayed on the display 4, and a movement of acursor to be displayed in accordance with the gazing points. The locusrepresented by the dashed line in FIG. 9 indicates the locus connectingthe gazing points by a user, which are specified based on the anglesignal output from the eye-ball movement detecting apparatus 2. Thelocus represented by the dashed line is a locus of the cursor to bedisplayed so as to reproduce the movement of the gazing point by theuser as it is. In this case, even while the user is intentionally gazingone point, the cursor is moving slightly. Also when the user moves theline of sight, the movement of the cursor is not smooth, and it isdifficult for the user to keep watching the display 4.

On the other hand, the locus represented by the solid line in FIG. 9 isa locus of the cursor to be displayed as a result of the processingroutine illustrated in the flowchart in FIG. 6 by the CPU 30 based onthe gazing points by the user resulting from the conversion. At thepoint G1 being the starting point and the point G2 being the end pointof the locus represented by the solid line in the FIG. 9, the state thatthe eyeball of the user is stopping is determined, and the cursor isdisplayed still. When the user has the intension to stop his/hereyeball, that is, the intension to gaze one point, the processingillustrated in the flowchart in FIG. 6 highly possibly determines thatthe eyeball is stopping even while the gazing point on the display 4 ismoving slightly in accordance with the movement of the eyeball of theuser. As a result, the cursor is displayed as stopping at one point.

In this way, performing the above processing by the CPU 30 allows thedetermination that the eyeball is stopping in accordance with thecharacteristic of the slight movement of the gazing point including theslight involuntary eye movement by each user. Thus, as illustrated inthe explanatory diagram in FIG. 9, the pointing device based oneye-controlled input can be implemented, which allows display of acursor naturally to a user.

The pointing device according to the present embodiment can implementnot only the cursor display processing as described above but also theoperation of clicking or double-clicking on an icon as illustrated inthe explanatory diagram in FIG. 9. For example, when the CPU 30 in thePC 3 determines that a gazing point of a user is stopping on a region ofan icon for a predetermined period of time or longer, the CPU 30determines that the icon has been selected. In this case, not only“select” but also “click operation” and “double-click operation” may beassociated with the cursor. Thus, the click operation or double clickoperation based on an eye-controlled input can be implemented. Forexample, menu icons corresponding to “select”, “click” and “doubleclick” are displayed on the display 4 in advance, and when the statethat the gazing point is on one of the menu icons and the eyeball isstopping there is determined, the corresponding processing may beassociated with the cursor, and it may be determined that the processingis performed at the gazing point where the state that the eyeball isstopping is determined next. Furthermore, an object such as a pen and abrush in a GUI as in Windows (registered trademark) may be associatedwith the cursor so that a rendering operation based on theeye-controlled input may be implemented.

Notably, the eyeball movement detecting apparatus 2 according to thepresent embodiment uses the cornea reflection technique to detect anangle. However, the present invention is not limited thereto but mayalternatively apply another technology such as EOG (electro-oculogram)and scleral reflection technique if the technology can detect the angleof the line of sight corresponding to the movement of the eyeball.

The moving object detecting apparatus is also applicable not only to apointing device, as described above, that detects a movement of a lineof sight of a human being and associates it with a two-dimensionalcursor movement on the display 4 but also to an apparatus thatdetermines that a one-dimensional or three-dimensional movement by amoving object is stopping.

For example, the present invention is applicable to a three-dimensionaltechnology in which, among movements of an arm or finger of a humanbeing, a rotation is detected by an acceleration sensor or a shift isdetected by an image sensor, an infrared ray sensor or the like, and arobot arm is moved so as to reproduce the detected movement of the armor finger. Such a robot arm can be used for a work in a space where itis difficult for a human being to stay or for a remote operation. Whenthe moving object detecting apparatus and/or method is applied to such arobot arm, the robot arm can be stopped when the state that an arm orfinger of a human being is stopping is determined without reflection ofshaking of the arm or finger even when the human being intends to stopthe arm or finger but the arm or finger shakes. In this way, the presentinvention is applicable to a robot arm that can determine that a part ofa body such as an arm or finger is stopping in accordance with thecharacteristic of shaking which varies due to an individual differenceand correct and reproduce a movement.

What is claimed:
 1. An object detection system, comprising: a receiveunit configured to receive an angle signal of a line of sight of a userto a display, wherein the angle signal of the line of sight of the usercorresponds to movement of an eyeball of the user; and a controllercoupled to the receive unit and configured to convert the received anglesignal to coordinates corresponding to gaze points of the user on thedisplay, wherein the controller is configured to: arbitrarily select twogaze points out of a plurality of most recently obtained gaze points andto calculate a circle, wherein a line that connects the two selectedgaze points represents a diameter of the circle; determine whetherremaining gaze points of the plurality of most recently obtained gazepoints are contained within the circle; responsive to a determinationthat the remaining gaze points are contained within the circle, identifythe circle as a containing circle and store a radius and a center of thecontaining circle in a memory; compare the containing circle to one ormore additional containing circles to identify a minimum containingcircle, wherein the minimum containing circle is a containing circlethat is identified with a smallest diameter; determine whether an areaof the minimum containing circle exceeds a specific minimum area; andresponsive to a determination that the area of the minimum containingcircle is within the specific minimum area, determine that a gaze of theuser is stationary.
 2. The system of claim 1, wherein the controller isconfigured to identify the one or more additional containing circles. 3.The system of claim 1, wherein the plurality of most recently obtainedgaze points comprise ten gaze points.
 4. The system of claim 1, whereinthe remaining gaze points comprise eight gaze points.
 5. The system ofclaim 1, wherein the controller is configured to cause the display todisplay a still cursor.
 6. The system of claim 1, wherein the controlleris configured to determine whether the plurality of gaze points arecontained in the minimum containing circle for a specific time.
 7. Thesystem of claim 1, wherein the angle signal represents an angle in ahorizontal direction from the user to the display and an angle in avertical direction from the user to the display about a reference linefrom the user to the display, wherein the reference line includes astraight line that vertically enters the display.
 8. The system of claim1, further comprising: an image capture unit configured to capture animage of the eyeball of the user, wherein the controller is coupled tothe image capture unit and configured to detect the angle signal of theline of sight of the user based on a center of a pupil in the capturedimage.
 9. The system of claim 8, wherein the image capture unit isconfigured to capture the image of the eyeball of the user at a specificfrequency.
 10. An object detection method, comprising: receiving anangle signal of a line of sight of a user to a display, wherein theangle signal of the line of sight of the user corresponds to movement ofan eyeball of the user; converting the received angle signal tocoordinates corresponding to gaze points of the user on the display;selecting two gaze points out of a plurality of most recently obtainedgaze points; calculating a circle, wherein a line that connects the twoselected gaze points represents a diameter of the circle; determiningwhether remaining gaze points of the plurality of most recently obtainedgaze points are contained within the circle; responsive to adetermination that the remaining gaze points are contained within thecircle, identifying the circle as a containing circle and storing aradius and a center of the containing circle in a memory; comparing thecontaining circle to one or more additional containing circles toidentify a minimum containing circle, wherein the minimum containingcircle is a containing circle that is identified with a smallestdiameter; determining whether an area of the minimum containing circleexceeds a specific minimum area; and responsive to a determination thatthe area of the minimum containing circle is within the specific minimumarea, determining that a gaze of the user is stationary.
 11. The methodof claim 10, further comprising identifying the one or more additionalcontaining circles.
 12. The method of claim 10, wherein the plurality ofmost recently obtained gaze points comprise ten gaze points.
 13. Themethod of claim 10, wherein the remaining gaze points comprise eightgaze points.
 14. The method of claim 10, further comprising updating aposition of a cursor to display a still cursor.
 15. The method of claim10, further comprising: capturing an image of the eyeball of the user;detecting the angle signal of the line of sight of the user based on acenter of a pupil in the captured image; and transmitting the detectedangle signal.
 16. The method of claim 10, further comprising determiningwhether coordinates corresponding to the plurality of most recentlyobtained gaze points are detected within a specific period of time. 17.A non-transitory computer-readable medium including computer-readableinstructions stored therein, the instructions being executable by aprocessor of a computing device, the instructions being executable to:cause the computing device to use an image acquisition unit to captureimages of an eyeball of a user and light directed from a cornea of theeyeball, wherein the images are captured at a rate of 30 frames persecond, and wherein the light directed from the cornea results fromprojection of near infrared light onto the eyeball by the imageacquisition unit; cause the computing device to process the images todetect angle signals representative of a line of sight of the userrelative to a display, wherein the angle signals of the line of sight ofthe user correspond to movement of the eyeball of the user; cause thecomputing device to convert the detected angle signals to coordinatescorresponding to gaze points of the user on the display; cause thecomputing device to arbitrarily select two gaze points out of ten mostrecently obtained gaze points and to calculate a circle, wherein a linethat connects the two selected gaze points represents a diameter of thecircle; cause the computing device to determine whether a remainingeight of the ten most recently obtained gaze points are contained withinthe circle; responsive to a determination that the remaining eight ofthe ten most recently obtained gaze points are contained within thecircle, cause the computing device to identify the circle as acontaining circle and to store a radius and a center of the containingcircle in a memory; cause the computing device to identify additionalcontaining circles by analysis of circles formed from combinations oftwo gaze points out of the ten most recently obtained gaze points; causethe computing device to identify a minimum containing circle, whereinthe minimum containing circle is a containing circle that is identifiedwith a smallest diameter; cause the computing device to determinewhether an area of the minimum containing circle exceeds a specificminimum area; and responsive to a determination that the area of theminimum containing circle is within the specific minimum area, cause thecomputing device to determine that a gaze of the user is stationary andto render a stationary cursor on the display.
 18. The non-transitorycomputer-readable medium of claim 17, wherein the instructions arefurther executable to cause the computing device to: determine whether asubsequently obtained gaze point is within the minimum containingcircle; and responsive to a determination that the subsequently obtainedgaze point is within the minimum circle, determine that the gaze of theuser is still stationary.
 19. The non-transitory computer-readablemedium of claim 17, wherein the instructions are further executable tocause the computing device to: determine whether a plurality ofsubsequently obtained gaze points are within the minimum circle; andresponsive to a determination that one or more of the plurality ofsubsequently obtained gaze points are within the minimum circle,determine that the gaze of the user is still stationary.
 20. Thenon-transitory computer-readable medium of claim 19, wherein theinstructions are further executable to cause the computing device to,responsive to a determination that all of the plurality of subsequentlyobtained gaze points are outside of the minimum circle, determine thatthe gaze of the user is moving.